Field
Embodiments of the disclosure relate generally to the field of fastener installation and more particularly to a method and apparatus for direct measurement of fastener strain during tightening using laser ablation to create shockwaves within the fastener and detecting reflection of the shockwaves for preload measurement.
Background
Mechanical fasteners such as threaded bolts and associated nuts used in joining of structures for various applications including the manufacture of aircraft are typically installed using a torque value. Torque measurements may be adversely affected by variability in friction losses in the bolt and nut interaction as well as interaction with intermediate structural surfaces and sealants and lubricants employed in the assembly process. Existing torque tool systems, processes and specifications are becoming more expensive to maintain since all measurable data is dependent on a torque value not actual preload or strain measurement in the bolt.
It is therefore desirable to provide a method and apparatus for direct strain or preload measurement in fastener bolts.